This invention relates to a power take-off assembly for a working vehicle in which a rear- or front-PTO shaft is particularly provided in addition to a mid-PTO shaft in a very simple manner whereby an essential part of the vehicle can be made common to a working vehicle having only a mid-PTO shaft and a working vehicle having a mid-PTO shaft and a rear- or front-PTO shaft.
There are disclosed in U.S. Pat. Nos. 5,099,936 and 5,901,605 techniques that a rear-PTO shaft is additionally provided to a working vehicle having a mid-PTO shaft in a simple manner.
Of these patents, U.S. Pat. No. 5,099,936 discloses a working vehicle in which a transmission casing having left and right rear wheel axles is disposed between left and right rear wheels and in which there is provided a mid-PTO shaft which extends from the inside of the transmission casing through a front wall of the casing. For providing a rear-PTO shaft, a rear cover of the transmission casing of a working vehicle having only a mid-PTO shaft is removed and, in place of it, a power take-off casing which includes in it a rear-PTO shaft extending rearwardly of the power take-off casing and a transmission mechanism for transmitting power to the rear-PTO shaft is mounted on a rear end of the transmission casing. An input member of the transmission mechanism is operatively connected to a final drive gear, which is rotatably mounted on the mid-PTO shaft, through a clutch which is shifted selectively to a position where the final gear is coupled only to the mid-PTO shaft, another position where the final gear is coupled to both of the mid-PTO shaft and the input member, and a further position where the final gear is coupled only to the input member.
U.S. Pat. No. 5,901,605 discloses a working vehicle in which there is provided a transmission casing including therein a mid-PTO shaft which extends from the inside of the transmission casing forwardly of the casing an electromagnetic clutch which is disposed between coaxially arranged input and output shafts for selectively coupling the shafts, and a speed reduction gearing which transmits power from the output shaft to the mid-PTO shaft. For converting a working vehicle having only a mid-PTO shaft into a working vehicle having a mid-PTO shaft and a rear-PTO shaft, a rear cover of the transmission casing is exchanged for a new rear cover and a transmission shaft in the reduction gearing is exchanged for a clutch shaft and, at the same time, positions of a part of gears in the reduction gearing are changed. The rear-PTO shaft is supported by the new rear cover and by a rear-PTO cover which is secured to a rear surface of the new rear cover, and there is provided on the clutch shaft a clutch which is shifted selectively to a position where power is transmitted only to the mid-PTO shaft, another position where power is transmitted to both of the mid-PTO shaft and the rear-PTO shaft, and a further position where power is transmitted only to the rear-PTO shaft.
Therefore, for converting a working vehicle having only a mid-PTO shaft into a working vehicle having a mid-PTO shaft and a rear-PTO shaft, each of the above-referenced U.S. patents requires removal or exchange of the rear cover of the transmission casing so that the converting operation is troublesome. Particularly, the rear cover of the transmission casing is used for supporting transmission shafts or gear-supporting shafts in the transmission casing, which makes the converting operation troublesome. The converting operation is very troublsome with respect to the power take-off assembly disclosed in U.S. Pat. No. 5,901,605 because it requires position-changing operation of a part of gears in the reduction gearing as well.
Accordingly, a primary object of the present invention is to provide a novel power take-off assembly for a working vehicle in which a rear- or front-PTO shaft is provided in a manner such that converting operation from a working vehicle having only a mid-PTO shaft into a working vehicle having a mid-PTO shaft and a rear- or front-PTO shaft can be made very easily. Another object of the invention is to provide a novel power take-off assembly for a working vehicle in which a rear- or front-PTO shaft is provided in a manner such that a working vehicle having only a mid-PTO shaft can be offered to numerous users requring no rear- or front-PTO function with a low cost.
The present invention relates to a power take-off assembly for a working vehicle in which a transmission casing (3) having left and right drive wheel axles (4a) is disposed between left and right drive wheels (4) and in which there is provided a mid-PTO shaft (9) which extends from the inside of the transmission casing (3) through an axial end wall (3a) of the transmission casing located at an inner side of the longitudinal direction of the vehicle. The power take-off assembly according to the present invention is characterized in:
that a power take-off casing (47) is mounted on an outer surface of an axial end wall (3c) of the transmission casing (3) located at an outer side of the longitudinal direction of the vehicle, the power take-off casing (47) including in it a second PTO shaft (12), which extends from the power take-off casing toward a direction opposite to the mid-PTO shaft (9), and a transmission mechanism (50) for transmitting power to the second PTO shaft (12);
that an input member (52) of the transmission mechanism (50) is operatively connected to a drive mechanism (46) for the mid-PTO shaft (9) in the transmission casing (3) through an opening (44) in the axial end wall (3c) in the transmission casing (3) located at the outer side of the longitudinal direction of the vehicle; and
that a clutch (60) for selectively cutting-off the transmission of power to the second PTO shaft (12) is provided.
The above-referenced second PTO shaft is a rear-PTO shaft extending rearwardly of the power take-off casing when the above-referenced drive wheels are left and right rear wheels between which the transmission casing is disposed, whereas the second PTO shaft is a front-PTO shaft extending forwardly of the power take-off casing when the drive wheels are left and right front wheels between which the transmission casing is disposed.
Because the power take-off assembly according to the present invention is structured such that, while the structure of the transmission casing (3) remains unchanged, a power take-off casing (47) including therein a second PTO shaft (12) and a transmission mechanism (50) therefor is mounted on the outer surface of an end wall (3c) of the transmission casing located at an outer side of the longitudinal direction of the vehicle and an input member (52) of the transmission mechanism is operatively connected to the drive mechanism (46) for the mid-PTO shaft (9) through an opening (44) in the axial end wall, the axial end wall (3c) is made common to a working vehicle having only a mid-PTO shaft and a working vehicle having a mid-PTO shaft and a second PTO shaft, so that the axial end wall can be used commonly to both kinds of the working vehicles for supporting transmission shafts or gear-supporting shafts. Accordingly, in converting a working vehicle having only a mid-PTO shaft into a working vehicle having a mid-PTO shaft and a second PTO shaft, removal or exchange of a rear cover corresponding to such an axial end wall, which is required in the above-referenced two U.S. patents, is no more required and the converting operation can be perfomed very easily, while the axial end wall is used for supporting shafts as it is, only by mounting the power take-off casing onto the outer surface of the axial end wall and by connecting the input member to the drive mechanism for the mid-PTO shaft. For converting a working vehicle having a mid-PTO shaft and a rear- or front-PTO shaft into a working vehicle having only a mid-PTO shaft, it is satisfactory that the power take-off casing (47) is removed and the above-referenced opening (44) in the axial end wall of the transmission casing is closed by a suitable cover member, so that a working vehicle having only a mid-PTO shaft can be offered to users at a very low cost. The clutch (60) for selectively cutting-off the transmission of power to the second PTO shaft (12) can be provided in any optional position of the transmission mechanism (50).
Preferably, the clutch (60) is operable to selectively drive the mid-PTO shaft (9) or the second PTO shaft (12). For achieving such a clutch with a simple structure, it is preferred that the input member (52) is arranged coaxially with the mid-PTO shaft (9), that the drive mechanism (46) includes a drive gear (58) which is rotatably mounted on the mid-PTO shaft (9) and is meshed with a gear (41) of driving side, and that the clutch (60) is structured such that it is shifted selectively to a condition where the drive gear (58) is coupled to the mid-PTO shaft (9) and to another condition where the drive gear (58) is coupled to the input member (52). Preferably, the clutch (60) is structured such that it is further shifted to a condition where the drive gear (58) is coupled to the mid-PTO shaft (9) and to the input member (52) at a same time. In this case, the mid-PTO shaft (9) and the second PTO shaft (12) can be driven to rotate at a same time.
Alternatively, it is preferred that the input member (52) is arranged coaxially with an intermediate drive shaft (40) which is provided in the drive mechanism (46) and is operatively connected to the mid-PTO shaft (9), that the drive mechanism (46) includes a drive gear (41A) which is rotatably mounted on the intermediate drive shaft (40) and is meshed with a gear (34) of driving side, and that the clutch (60) is structured such that it is shifted selectively to a condition where the drive gear (41A) is coupled to the intermediate drive shaft (40) and to another position where the drive gear (41A) is coupled to the input member (52). This structure also allows to drive selectively the mid-PTO shaft (9) or the second PTO shaft (12). Preferably, the clutch (60) is structured such that it is further shifted to a condition where the drive gear (41A) is coupled to the intermediate drive shaft (40) and to the input member (52) at a same time. In this case, the mid-PTO shaft (9) and the second PTO shaft (12) can be driven to rotate at a same time.
It is dangerous for an operator to get out of the vehicle while the mid-PTO shaft is rotating. In a preferred embodiment, there is further provided a sensor switch (67) for sensing coupling conditions of the drive gear (58) to the mid-PTO shaft (9) or coupling conditions of the drive gear (41A) to the intermediate drive shaft (40) such that the sensor switch (67) is operated by a shifter member (63) for shifting the clutch (60). When the sensor switch is in an operated condition, the operator will stop the rotation of mid-PTO shaft by the operation of clutch so as to avoid a danger in advance.
It is often the cases that the second PTO shaft or the rear- or front-PTO shaft is used for driving an auxiliary implement of a high load. According to a preferred embodimemt of the present invention, the input member is composed of an input gear (52) mounted on a shaft (51; 73) which is arranged in parallel with the second PTO shaft (12) and is supported by the power take-off casing (47). Further, the transmission mechanism (50) comprises a speed-reduction gear train for transmitting power from the input gear (52) to the second PTO shaft (12) at a reduced speed of rotation.
In the power take-off assembly according to the present invention, the number of PTO shafts can be increased in the following manner. That is, the input gear (52) is fixedly mounted on the shaft (73) for mounting the input gear and this shaft is extended outwardly from the power take-off casing (47) toward a direction same as the second PTO shaft (12) so as to provide a third PTO shaft (73). The third PTO shaft can be used, for example, to drive a generator which feeds electric power to an electrically driven implement such as a chain saw.